Flush on write to floppy images as well.

src/floppy/fdd_86f.c

@@ -3225,6 +3225,8 @@ d86f_writeback(int drive)
         free(dev->filebuf);
     }
 #endif
+
+    fflush(dev->fp);
 }
 
 void

src/floppy/fdd_imd.c

@@ -549,6 +549,8 @@ imd_writeback(int drive)
             }
         }
     }
+
+    fflush(dev->fp);
 }
 
 static uint8_t

src/floppy/fdd_img.c

@@ -431,6 +431,8 @@ write_back(int drive)
         if (fwrite(dev->track_data[side], 1, size, dev->fp) != size)
             fatal("IMG write_back(): Error writing data\n");
     }
+
+    fflush(dev->fp);
 }
 
 static uint16_t